A touch panel or a touchscreen is an electronic component composed of a combination of a display and a position detector. A touch on a touch panel with a finger or a pen can operate an electronic device. A touch panel is used, for example, in digital information equipment including ATMs at financial institutions such as banks, vending machines, mobile phones, personal digital assistants (PDAs), digital audio players, handheld game consoles, tablet personal computers, photocopiers, fax machines, car navigation systems and so on.
Input operation made via a touch panel sometimes leaves scratches on the surface and/or breaks the internal working due to the pressure applied. In order to prevent these, a touch panel is covered with a transparent protective plate on the surface of the touch panel. Protective plates made of tempered glass are widely used. And from the viewpoint of workability and weight reduction, protective plates made of a transparent resin are being researched. Such protective films are demanded to be lustrous, resistant to scratches, resistant to impact, and the like.
A polycarbonate resin is a resin suitable for use to produce a molded article excellent in impact resistance. A methacrylic resin is a resin suitable for use to produce a molded article that is highly lustrous and excellent in scratch resistance. When a polycarbonate resin and a methacrylic resin are subjected to heat melt molding at the same time (coextrusion, for example), a multilayer plate having a layer of the polycarbonate resin and a layer of the methacrylic resin can be produced. Heat melt molding of a resin, however, leaves a considerable amount of strain stress in the resulting molded article. The strain stress thus left in the molded article is called residual stress, and a molded article having residual stress warps and/or shrinks due to heat. Warpage due to residual stress presents a problem particularly in a molded article in a plate form, such as the multilayer plate. In order to decrease residual stress in a molded plate and inhibit warpage, a method is known where the rotation speed of a cooling roll used in extrusion is regulated (see Patent Document 1).